The present invention relates generally to an apparatus for and method of performing spectroscopic analysis on an article. Specifically, the present invention is directed to an apparatus for and method of performing Fourier transform infra-red (FTIR) spectroscopy on non-planar articles.
The analysis of an article serves a myriad of goals. Article analysis is used in, for example, quality control, defect detection, corrosion recognition and surface coating examination. Many types of articles are suitable for analysis, including, for example, medical devices, weapons, fuel injectors and various other articles of manufacture. FTIR spectroscopy is one method of analyzing such articles.
Present FTIR spectroscopy, however, cannot readily analyze non-planar articles, such as tubes or apertures. Present FTIR spectroscopy apparatuses are either: (1) limited to the analysis of planar surfaces; or (2) limited to the analysis of identical tubular articles (i.e. tubular articles with identical size, shape and orientation). Present FTIR spectroscopy apparatuses in the first category (i.e. limited to the analysis of planar surfaces) require the dissection of non-planar articles to perform such an analysis. The non-planar articles must be cut open and examined as a flat, planar surface. The dissection of the non-planar article to perform the analysis is clearly destructive testing. The article must be discarded after testing. It cannot be used again.
U.S. Pat. No. 5,088,821 to Milosevic demonstrates an FTIR spectroscopy analysis system limited to analyzing planar surfaces. The patent discloses a spectrometer 10 with at least one remote terminal 40, 60 housing a sample 43, 65. The system also utilizes radiation piping means 25, 26 to selective pipe radiation from the spectrometer to the remote terminals. FIG. 5 demonstrates a planar sample 43 in barrel ellipsoid terminal 40. FIG. 6 demonstrates a planar sample 65 in fixed angle external reflection terminal 60.
Present FTIR spectroscopy apparatuses in the second category (i.e. that allow testing of non-planar articles) have severe limitations. These apparatuses are limited to analysis of identically sized non-planar articles. The apparatuses cannot adapt to articles of varying sizes, shapes or orientations. Furthermore, the present FTIR spectroscopy apparatuses in the second category are limited to articles having a short bore and/or a small length.
The apparatuses in the second category also have problems with the attenuation of the light beam, causing a low signal-to-noise ratio. Furthermore, the apparatuses are not adapted to analyze articles in situ. The apparatuses require the removal of the article from service and the placement of the article within the light path.
Report number SAND87-8241 demonstrates an FTIR spectroscopy analysis system limited to the analysis of identical tubular articles. The report describes the analysis of stainless steel tubes (specifically tubing having a length of 25-100 mm and an inner diameter of 1 mm; and a length of 25 mm and an inner diameter of 0.7 mm) prior to a welding process. The operator places the tube in a jig mounted on a translation stage. The tube is situated between two lenses. The first lens focuses the IR beam on the entrance of the tube. The second lens collects the beam exiting the tube. The optics interface with an FTIR spectrometer to analyze the light beam.
Clearly, there is room for improvement in the art.